Selective etching of reactor surfaces

ABSTRACT

Compositions, methods, and systems permit selectively etching metal oxide from reactor metal parts (e.g., titanium and/or titanium alloys). The etching composition comprises an alkali metal hydroxide and gallic acid. The method is useful for cleaning reaction chambers used in the deposition of metal oxide films such as aluminum oxide.

BACKGROUND

1. Technical Field

This application is generally related to thin film manufacturing, andmore particularly, to the cleaning of reactors used in depositing thinfilms.

2. Description of the Related Art

In the manufacture of integrated devices, thin films are deposited orformed on substrates in a reaction chamber or reactor, for example, bychemical vapor deposition (CVD) or atomic layer deposition (ALD). Inthese deposition processes, the film materials are also deposited onother surfaces, for example, on the walls and other exposed surfaces ofthe reaction chamber, thereby contaminating these surfaces. Over time,these materials accumulate and build up, eventually flaking, shedding,and/or delaminating particles from the surface of the reaction chamber.Particles that land on a surface of a substrate, for example, eitherfalling on the surface or carried in a gas stream, can cause problems inthe manufacturing process, for example, by reducing the yield and/orreproducibility of the process. Periodically cleaning the contaminantsfrom the reaction chamber can reduce these problems.

One method for cleaning a reaction chamber is by in situ etching cyclesusing one or more cleaning cycles of suitable etchants. In situ cleaningreduces the need to remove, replace, and/or requalify a contaminatedreaction chamber. In cases in which the etch rates are high, in situetching can be performed as often as necessary without significantlyaffecting the tool's throughput. Lower etch rates can reduce throughput,however. Moreover, in some cases in situ etching exhibits one or moredrawbacks, for example, significantly etching one or more components ofthe reaction chamber, causing substrate contamination, and/or causingenvironmental, health, and safety (EHS) problems. Consequently, in somecases, in situ cleaning is not feasible.

Another option for cleaning reaction chambers is ex situ cleaning, inwhich the contaminated components are removed from service for cleaning.“Bead blasting” is a form of ex situ cleaning by mechanical abrasion inwhich a stream of an abrasive grit, for example, alumina, zirconia,glass, silica, SiC, or other suitable material, is impinged against asurface-to-be-cleaned, for example, using a high-pressure fluid stream.Bead blasting has several shortcomings, for example, damage can becaused to the reaction chamber components by the cleaning process,thereby reducing their lifetimes. Bead blasting is a “line of sight”process, resulting in difficultly in cleaning high aspect ratiocomponents. Due to an inability to visually monitor the removal of thecontaminant(s), an endpoint not apparent, such that, when thecontaminant is removed and the underlying material is reached; there isa chance of missing a contaminated area. Bead blasting can also causecontamination of the cleaned part by the abrasive material. Contaminantsthat are as hard or harder than the abrasive material cannot easily beremoved by bead blasting. Bead blasting also entails high cost and lowreproducibility.

SUMMARY OF THE INVENTION

Compositions, methods, and systems permit selectively etching metaloxides from metal chamber surfaces. The method is useful for cleaningreaction chambers used in the deposition of metal oxide films.

In one embodiment, a method is provided for selectively etching metaloxide from a metal part of a semiconductor reactor. The method includescontacting a surface of a metal part with an alkaline etchant. A metaloxide is present on the surface of the metal part. The alkaline etchantis effective for etching the metal oxide. While the metal part issusceptible to chemical attack by the alkaline etchant, the surface ofthe metal part is also contacted part with an inhibitor effective forinhibiting chemical attack of the metal part by the alkaline etchant.

In another embodiment, a method is provided for ex situ wet cleaningaluminum oxide from a titanium or titanium alloy surface of a depositionreactor used for depositing aluminum oxide. The method includescontacting with an etchant a titanium or titanium alloy surface of adeposition reactor on which a layer of aluminum oxide is deposited,wherein the etchant comprises at least one of sodium hydroxide andpotassium hydroxide. The method further includes contacting the titaniumor titanium alloy surface with an inhibitor comprising a polyhydroxybenzene compound. The titanium or titanium alloy surface is alsocontacted with a stabilizer comprising borate species.

In another embodiment, an etching composition is provided forselectively cleaning metal oxide from metal parts. The compositionincludes an alkaline etchant in an amount effective to etch metal oxidefrom over a metal part. The composition also includes an inhibitor in anamount effective to inhibit etching of the metal part by the alkalineetchant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart illustrating an embodiment of a method forselectively etching metal oxide from metal chamber parts.

FIG. 2 schematically illustrates an embodiment of a test sample usefulfor evaluating the etching of aluminum oxide from titanium.

FIG. 3A is a FESEM of area 1 of a test sample etched in the absence ofgallic acid. FIG. 3B is a FESEM of area 2 of the same test sample.

FIG. 4A is a FESEM of area 1 of a test sample etched in the presence ofgallic acid. FIG. 4B is a FESEM of area 2 of the same test sample.

FIGS. 5A and 5B are FESEM images of a planar face of a test sampleetched in the presence of gallic acid.

FIG. 6 is an FESEM image of a planar face of a test sample etched in thepresence of gallic acid identifying areas at which EDS was performed.

FIGS. 7A-7C are EDS spectra of the areas identified in FIG. 6.

FIGS. 8A and 8B graphically illustrate aluminum oxide etching rates fordifferent etchant concentrations.

FIG. 9 graphically illustrates aluminum oxide etching rates fordifferent etchant concentrations and temperatures.

FIGS. 10A-10C are FESEM images of a test sample etched in the absence ofgallic acid.

FIG. 11 is an FESEM image of a test sample etched in the presence ofgallic acid.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS

Described herein is a composition, method, and system for cleaningbase-etchable contaminants from metal parts or components ofsemiconductor reactors, particularly deposition chambers. CVD and/or ALDreaction chambers often comprise titanium and/or titanium alloycomponents, for example, Pulsar® ALD reaction chambers (ASMInternational, Bilthoven, the Netherlands). Other susceptible metalsurfaces in many deposition chambers include stainless steel (e.g., 316Land 304), nickel and nickel alloys. For example, ALD deposition of metaloxides such as aluminum oxide (alumina, Al₂O₃) in a reaction chamberwill also deposit layers of aluminum oxide on portions of the reactionchamber. These layers are often non-uniform, for example, from about 150nm to thousands of nanometers thick, depending on factors including thelocation of the surface in the reaction chamber, reaction chamberdesign, the number of deposition cycles, the number of substratesprocessed, and other processes performed in the reaction chamber. Thesefilms potentially flake, shed, spall, or delaminate to formcontaminating particles. In particular, aluminum oxide is difficult toclean from reactor surfaces because it is both extremely hard andresistant to many etch chemistries. Other metal oxides deposited in suchALD or CVD chambers for semiconductor processing include hafnium oxide(HfO₂), zirconium oxide (ZrO₂) and hafnium zirconium oxide(Hf_(x)Zr_(y)O_(z)). Removal of such metal oxides can also be difficultwithout damage to the underlying metal surfaces.

Accordingly, the present disclosure provides methods for periodicremoval of deposited metal oxide from reactor walls, typically ex situafter multiple deposition cycles. In addition to metal oxide that isincidentally deposited on deposition chamber parts in the course ofdepositions on substrates, metal oxide is also used as a protectivepassivation layer or a lift-off layer on reactor chamber surfaces.Periodically, such layers also need to be removed for refreshing, andthe methods described herein can also be employed to remove suchpassivation or lift-off layers periodically from reactor metal parts(whether for deposition reactors or other reactors).

An etching composition comprises an etchant suitable for etching aselected contaminant and a modifier that increases the etchingselectivity between the contaminant and the material of asurface-to-be-cleaned. In a preferred embodiment, the selectedcontaminant comprises aluminum oxide, the etching composition comprisesan aqueous composition comprising a base or alkali, and thesurface-to-be-cleaned comprises titanium and/or titanium alloy. In someembodiments, the modifier comprises a compound that inhibits etching oftitanium and/or titanium alloy, referred to herein as an “inhibitor.” Inother embodiments, the contaminant to be removed is hafnium oxide,zirconium oxide or mixtures thereof. The surface-to-be-cleaned can alsobe stainless steel (e.g., 316L and 304), nickel and/or nickel alloys.

In some embodiments, the base etchant comprises a hydroxide of analkaline metal, for example, lithium, sodium, potassium, rubidium,cesium, and combinations thereof. In preferred embodiments, the base issodium hydroxide, potassium hydroxide, or combinations thereof. Morepreferably, the base is potassium hydroxide. The concentration of thebase is from about 0.1 M to about 10 M, preferably, from about 0.2 M toabout 5 M, more preferably, from about 0.5 M to about 1 M. In somepreferred embodiments, the concentration is about 0.5 M, about 1 M, orabout 5 M. Higher base concentrations generally correlate with fasteretching of aluminum oxide or other metal oxide. In general, for a givenetch rate, higher etchant concentrations will be desirable for etchingZrO₂, HfO₂, and/or Hf_(x)Zr_(y)O_(z) as compared to Al₂O₃.

In some preferred embodiments, the modifier that provides highselectivity comprises an inhibitor selected from gallic acid (seeFormula 1 below), analogs of gallic acid, salts thereof, otherpolyhydroxy benzene compounds (e.g., polyphenols, pyrogallol, catechol),combinations thereof, and the like. Those skilled in the art willunderstand that gallic acid will form a salt of gallate anion underbasic conditions. The terms “gallic acid” and “gallate” are both usedherein to refer to the species present in the etching composition.Preferably, gallic acid is added from about 1:50 to about 1:1 molarratio compared with the base, more preferably, from about 1:20 to about1:5, most preferably, about 1:10.

Preferably, the composition further comprises one or more borate anionspecies, for example, borate (BO₃ ³⁻), metaborate (BO₂ ⁻), tetraborate(B₄O₇ ²⁻), and the like, which is added by way of any suitable sourcecompound, for example, borate salts, boric acid, borate esters,combinations thereof, and the like. A preferred borate source is borax(sodium tetraborate decahydrate, Na₂B₄O₇.10H₂O). Those skilled in theart will appreciate that a complex mixture of borate species is formedunder basic conditions, for example, borate, diborate, triborate,tetraborate, and higher borates. Accordingly, the term “borate” as usedherein refers to all of the borate anions present in a composition. Theconcentration of borate species is with reference to the quantity of theborate precursor added rather than the actual concentrations of thespecies in solution. It is believed that borate stabilizes the gallicacid against oxidation. Preferably, the molar ratio of gallic acid toborate is from about 1:10 to about 10:1, more preferably, from about 1:2to about 2:1, most preferably, about 1:1.

Some embodiments of the etching composition comprise other additivesknown in the art, for example, surfactants, dispersants, chelatingagents, viscosity modifiers, abrasives, combinations thereof, and thelike. Suitable surfactants include anionic, cationic, and nonionicsurfactants known in the art, for example, sulfonates, ammonium salts,polyethoxylates, combinations, and the like. Suitable dispersantsinclude those derived from ammonia, amines, alkanolamines, bases,combinations and the like, for example, triethanolamine. Surfactants,dispersants, and/or chelating agents can improve cleaning bysolubilizing and/or suspending contaminants and etching by-products, aswell as providing improved wetting of the surface-to-be-cleaned.Viscosity modifiers, thixotropic agents, and/or rheology modifiers areuseful in formulating gels and/or pastes, which permit the etchingformulation to cling to non-horizontal surfaces, for example. Abrasivesprovide a physical cleaning effect suitably activated, for example, bymechanical action, ultrasound, agitation, combinations, or the like.

FIG. 1 is a flowchart illustrating an embodiment of a method 100 forcleaning titanium and/or titanium alloy surfaces contaminated withmaterials comprising aluminum oxide. As discussed above, the etchingcomposition is also useful for etching zirconium oxide, hafnium oxide ormixtures thereof from stainless steel, nickel or nickel alloys.

In step 110, the surface-to-be-cleaned is optionally prepared foretching. For example, in some embodiments, one or more components of areaction chamber are disassembled, for example, to provide access to asurface-to-be-cleaned. Some embodiments comprise a precleaning step, forexample, to remove lubricants, sealants, and/or greases by any meansknown in the art. Those skilled in the art will understand that theparticular precleaning conditions will depend on the particular materialto be removed. Some embodiments include a masking step, for example, toprevent contact of a masked surface with the etching composition.

In step 120 the surface-to-be-cleaned is contacted with an etchingcomposition as described herein by any method known in the art, forexample, by immersing, brushing, spraying, dipping, combinationsthereof, and the like. Some embodiments use a high pressure jet of theetching composition onto the surface to be cleaned. As noted above, theetch rate of aluminum oxide generally increases with the baseconcentration. Higher temperatures also increase the etch rate. Suitabletemperatures include from about 0° C. to about 100° C., preferably, fromabout 20° C. to about 90° C., more preferably, from about 50° C. toabout 80° C. In some embodiments, etch rates of aluminum oxide are atleast about 2 μm/hr, preferably, at least about 8 μm/hr, morepreferably, at least about 17 μm/hr. In some embodiments, the underlyingtitanium surface is oxidized at less than about 1 μm/hr, preferably,less than about 0.3 μm/hr, more preferably, less than about 0.1 μm/hr.Selectivities between aluminum oxide and titanium are at least about20:1, preferably, at least about 30:1, more preferably, at least about40:1. The skilled artisan will appreciate that etch selectivityrepresents the ratio of etch rates for different materials exposed tothe etchant.

Etching times will depend on the thickness and nature of the aluminumoxide film(s), as well as the etching rate. As discussed above, filmthicknesses can vary on a single component. Because the selectivity ofthe etching composition is high, in some embodiments, the etchingcomposition may contacted with the surface-to-be-cleaned for much longerthan necessary for etching the aluminum oxide without significantlyoxidizing the titanium surface. Suitable etching times can be greaterthan about 1 hr, greater than about 5 hrs, or greater than about 10 hrs,depending upon the metal oxide thickness to be removed.

In some embodiments, the etching is assisted mechanically, for example,by ultrasound and/or by mechanically abrading the surface-to-be-cleaned,for example, using an abrasive pad and/or brush. Fresh etchingcomposition can be replenished at the surface-to-be-cleaned by agitatingor circulating the composition, for example, using a stirring deviceand/or fluid pump.

As discussed above, some embodiments of the etching composition compriseabrasive particles. In these embodiments, mechanical cleaning isinitiated by, for example, high pressure washing, ultrasound, agitation,combinations thereof, and the like.

In step 130, the etching is terminated, for example, by rinsing with anysuitable agent, for example, with deionized water, distilled water,alcohols, ammonia, organic solvents, combinations thereof, and the like.The inhibitor for selectivity may be chemisorbed on the metal parts andshould be removed to restore the natural passivation layer of titaniumat the surface and to prevent potential contamination of the reactor,which can impact adhesion of subsequent depositions on the chambersurfaces or contaminate substrates on which the layers are beingdeposited. Removal of chemisorbed inhibitor (e.g., gallic acid) can beaided by exposure to oxidizing treatments, such as ozonated deionizedrinse, plasma treatments, peroxide, monoperoxysulfate or diperoxysulfaeor peroxy inorganic oxidants.

In some embodiments, the cleaned surface is further processed, forexample, by polishing. The cleaned surface is inspected to assess theeffectiveness of the cleaning as well as the condition of the component.Components are refurbished, if necessary, for example, by refacing.Components passing inspection are then requalified, if necessary, andreturned to service.

Contacting titanium with a basic etchant in the absence of an inhibitortends to oxidize the titanium, forming a porous, surface layer oftitanium dioxide (TiO₂, titania). This layer of titanium dioxide is notself passivating, that is, does not prevent further oxidation of themetal. Consequently, continued exposure to the base etchant results in athicker layer of titanium dioxide. In addition, the pores tend to growover time. Contact with hot, concentrated base accelerates theoxidation.

When present on reactor surfaces, this porous oxide layer negativelyimpacts process throughput and reproducibility. Process gases areretained in the pores in the oxide, increasing purge time becauseremoval of the gases is limited by diffusion. The porous surface alsohas a larger surface area than a comparable unoxidized titanium surface,increasing the quantity of process gases adsorbed on the surface,thereby increasing the consumption of process gases and processingtimes. These concerns are especially true for ALD deposition processes.Because titanium dioxide is less dense than titanium, the dimensions ofthe component will change, which can alter critical dimensions. Thetitanium dioxide layer is also susceptible to flaking and/or spalling,thereby generating contaminating particles. Even if the oxide layer isremoved, the oxidation of the titanium alters the dimensions of thecomponent, changing critical features, thereby reducing the lifetime ofthe component.

It is believed that the inhibitor, for example, gallic acid, forms alayer on the surface of titanium or titanium alloy that resistsoxidation by the etchant.

Similarly, damage to other metal reactor parts can also occur whenetching metal oxides from over other metals (e.g., stainless steel,nickel or nickel alloys), without adequate selectivity.

EXAMPLE 1 Effect of Gallic Acid on Etch Rates

FIG. 2 illustrates a test sample 200 comprising a titanium sheet 210(2.3 cm×2.8 cm×1 mm) and alumina strips 220. Two sets of test sampleswere formed. One sample of each set had a thick alumina layer (˜49 μm),and one had a thin alumina layer (˜7 μm). The test samples were cleanedwith isopropanol, rinsed with distilled water, and dried with nitrogenbefore etching. Etching was performed in double-walled beakers in atemperature controlled water bath. One set of test samples was etched inan aqueous solution of 0.5 M KOH at 80° C. for 40 min. The other set oftest samples was etched in an aqueous solution of 0.5 M KOH/0.05 Mgallic acid/0.05 M sodium tetraborate (Na₂B₄O₇) at 80° C. for 40 min.Unless otherwise specified, all reagents were purchased from AldrichChemical Co. (Milwaukee, Wis.) and used without purification. Afteretching, the test samples were rinsed with distilled water and dried ina nitrogen stream. Alumina step heights were measured before and afteretching by profilometry (KLA-Tencor, San Jose, Calif.). Results aresummarized in TABLE I.

TABLE I Height pre Etchant etch (μm) Height post etch (μm) Difference(μm) KOH 48.9 40.3 8.6 KOH 7.2 0 7.2 KOH/gallic acid 54.4 46.5 7.9KOH/gallic acid 7.4 0 7.4

The etch rate of aluminum oxide in the absence of gallic acid was 12.9μm/hr, and in the presence of gallic acid was 11.8 μm/hr. Gallic aciddid not significantly affect etch rates of aluminum oxide.

EXAMPLE 2 Field Emission Scanning Electron Microscopy

Field emission scanning electron microscopy (FESEM) was performed on theetched test samples from Example 1 to ascertain the effect of etching onthe surface morphology. An edge of each sample was polished with 280,then 1200 grit emery paper before imaging. Images were acquired at Area1 (titanium not covered by Al₂O₃ before etching) and Area 2 (titaniumcovered by Al₂O₃ before etching) as illustrated in FIG. 2.

FIG. 3A was taken at Area 1 of a sample etched in the absence ofgallate. An oxide layer was formed on the surface of the titanium. Theoxide layer was very thin and was not visible from the edge.Consequently, the sample was tilted to provide a better view. The edgebetween the top and side of the sample is indicated by the dark line.With an exposure of only 40 minutes, the oxide layer is thin and notcontinuous. Accelerating voltage was 5 kV; magnification: 40,000×. FIG.3B was taken at Area 2 of the same sample. The titanium surface exposedby the etching showed a series of bumps, indicating etching of theunderlying titanium after removal of the alumina in this area.Accelerating voltage: was 5 kV; magnification: 60,000×.

FIG. 4A was taken at Area 1 of a sample etched in the presence ofgallate. A film formed on the surface of the sample that does not appearto be porous titanium dioxide. Accelerating voltage was 5 kV;magnification: 40,000×. FIG. 4B was taken at Area 2 of the same sample.A film formed on the surface of the titanium appears similar to the filmin FIG. 4A, which does not appear to be porous titanium dioxide.Accelerating voltage was 5 kV, magnification: 60,000×.

Titanium oxide formed on samples etched absent gallate. Non-poroussurfaces were left on samples etched in the presence of gallate. Thus,gallic acid inhibits porous layer formation but does not influence theetch rate of alumina in KOH solution.

EXAMPLE 3 Characterization of Titanium Surface after Etching

Test samples with 7 μm thick aluminum oxide layers were prepared asdescribed in Example 1 and etched in a 0.5 M KOH, 0.05 M gallic acid,0.05 M Na₂B₄O₇ etching solution at 80° C. for 1 hr. The sample wasrinsed with distilled water and edge-polished as described in Example 2.Profilometry indicated complete etching of the aluminum oxide.

FESEM images of the planar face of the etched area formerly under thealuminum oxide are provided in FIGS. 5A and 5B. Accelerating Voltage was5.0 kV; magnification: 1000×.

Energy dispersive spectroscopy (EDS) X-ray microanalysis was alsoperformed at three locations formerly covered by aluminum oxide,designated as 1, 2, and 3 in FIG. 6, with the corresponding EDS spectraillustrated in FIGS. 7A-7C, respectively. These spectra revealsubstantially no aluminum remained on the sample indicating that theetching completely removed the aluminum oxide layer.

EXAMPLE 4 Aluminum Oxide Etch Rates

Two test samples were prepared and etched as described in Example 1.Etching was performed at 65° C. One experiment used 0.5 M KOH in theetching composition and the other used 1 M KOH. The thickness of thealuminum oxide layers on the top and bottom of the sample was monitoredby profilometry. Results are tabulated in TABLE II and illustratedgraphically in FIGS. 8A and 8B. Etching rates were similar for bothconcentrations of KOH in these experiments.

TABLE II 0.5 M KOH 1 M KOH Time Top (μm) Bottom (μm) Top (μm) Bottom(μm) 0 54.60 49.60 51.13 50.25 1 45.75 41.82 42.39 42.86 1.5 41.70 38.4039.67 37.83 2 38.96 37.73 35.20 34.24

In another set of experiments, etching rates were measured for 0.5 M and1 M KOH at 50° C., 65° C., and 80° C. Results are tabulated in TABLE IIIand illustrated in FIG. 9.

TABLE III Etch Rate Temperature in 0.5 M KOH (μm/hr) Etch Rate in 1 MKOH (μm/hr) 50 — 2.8 65 7.7 8.0 80 13 17

These results indicate that higher etch rates can be obtained at higherKOH concentrations and higher temperatures.

EXAMPLE 5 Effect of Hydroxide on Titanium

Titanium samples were cleaned by rinsing with distilled water,isopropanol, and distilled water; sonicating in distilled water; rinsingwith distilled water, isopropanol, and distilled water; soaking in 10%HNO₃ for 1 min; and rinsing in distilled water. Samples were then etchedin 0.5 M KOH (no gallate) for 2 hr or 4 hr as described in Example 1,then rinsed within distilled water and dried with nitrogen. An edge waspolished as described in Example 2 for FESEM analysis.

FIG. 10A is an FESEM image of an edge of a sample etched for 2 hrshowing a layer of titanium dioxide about 3 μm thick and the underlyingtitanium. The titanium dioxide layer has a porous honeycomb structure.Titanium dioxide was formed at about 1.5 μm/hr (250 Å/min). Acceleratingvoltage was 5 kV, magnification: 20,000×.

FIG. 10B is an FESEM image of an edge of another sample etched for 2 hr.In this sample, the thickness of titanium oxide layer is not uniform,but ranges from about 1 μm to about 3 μm. Again, the structure is aporous honeycomb. Accelerating voltage was 5 kV; magnification: 20,000×.

FIG. 10C is an FESEM image of an edge of a sample etched for 4 hr. Inthis sample, the thickness of titanium oxide layer is from about 5 μm toabout 6 μm. The pores in this sample appear to be larger than the poresof the 2 hr samples. Accelerating voltage was 5 kV, magnification:15,000×.

EXAMPLE 6 Effect of Hydroxide with Gallate on Titanium

Titanium samples were cleaned and etched as described in Example 5 using0.5M KOH, 0.05 M gallic acid, 0.05 M Na₂B₄O₇ at 80° C. for 1 hr, thenrinsed, dried, and edge polished. FIG. 11 is an FESEM image of an edgeof a sample showing a surface layer and underlying titanium. The surfacelayer is relatively thinner and smoother than the oxide layers ofExample 5. The surface layer is also not porous. This layer is believedto be a gallic acid or gallate layer, which protects the underlyingtitanium layer from chemical attack.

The embodiments illustrated and described above are provided only asexamples of certain preferred embodiments. Various changes andmodifications can be made to the embodiments presented herein by thoseskilled in the art without departure from the spirit and scope of thedisclosure, which is limited only by the appended claims.

1. A method for selectively etching metal oxide from a metal part of asemiconductor reactor, the method comprising: contacting a surface of ametal part with an alkaline etchant, wherein a metal oxide is present onthe surface of the metal part, the alkaline etchant is effective foretching the metal oxide, and the metal part is susceptible to chemicalattack by the alkaline etchant; contacting the surface of the metal partwith an inhibitor effective for inhibiting chemical attack of the metalpart by the alkaline etchant.
 2. The method of claim 1, wherein themetal oxide comprises at least one of hafnium oxide and zirconium oxide.3. The method of claim 1, wherein the metal part comprises at least oneof stainless steel, nickel and nickel alloys.
 4. The method of claim 1,wherein the metal part comprises at least one of titanium and a titaniumalloy.
 5. The method of claim 1, wherein the alkaline etchant comprisesan alkali metal hydroxide.
 6. The method of claim 5, wherein the alkalimetal hydroxide comprises at least one of sodium hydroxide and potassiumhydroxide.
 7. The method of claim 1, wherein the inhibitor comprises apolyhydroxy benzene compound.
 8. The method of claim 7, wherein theinhibitor comprises gallic acid.
 9. The method of claim 1, furthercomprising contacting the surface of the metal substrate with astabilizer effective to stabilize the inhibitor.
 10. The method of claim9, wherein the stabilizer comprises borate species.
 11. The method ofclaim 1, wherein at least a portion of a contacting step is performed atfrom about 0° C. to about 100° C.
 12. The method of claim 1, wherein themetal oxide is aluminum oxide and contacting the surface of the metalpart with the alkaline etchant and the inhibitor comprises etching thealuminum oxide at an etch rate of least about 2 μm/hr.
 13. The method ofclaim 12, wherein the etch rate of the aluminum oxide is at least about8 μm/hr.
 14. The method of claim 12, wherein contacting the surface ofthe metal part with the alkaline etchant and the inhibitor comprisesetching the metal part at an etch rate of less than 1 μm/hr.
 15. Themethod of claim 1, wherein contacting the surface of the metal part withthe alkaline etchant and the inhibitor comprises selectively etching themetal oxide from over the metal part with an etch selectivity of atleast 20:1.
 16. The method of claim 15, wherein the etch selectivity isat least 30:1.
 17. The method of claim 1, wherein the metal part is aninternal surface of a component of a chemical vapor deposition or atomiclayer deposition reaction chamber used in the deposition of aluminumoxide.
 18. The method of claim 1, further comprising removing theinhibitor from the metal part by an oxidizing treatment.
 19. A methodfor ex situ wet cleaning aluminum oxide from a titanium or titaniumalloy surface of a deposition reactor used for depositing aluminumoxide, the method comprising: contacting with an etchant a titanium ortitanium alloy surface of a deposition reactor on which a layer ofaluminum oxide is deposited, wherein the etchant comprises at least oneof sodium hydroxide and potassium hydroxide; contacting the titanium ortitanium alloy surface with an inhibitor comprising a polyhydroxybenzenze compound; and contacting the titanium or titanium alloy surfacewith a stabilizer comprising borate species.
 20. The method of claim 19,wherein the inhibitor comprises gallic acid.
 21. An etching compositionfor selectively cleaning metal oxide from metal parts, comprising: analkaline etchant in an amount effective to etch metal oxide from over ametal part; and an inhibitor in an amount effective to inhibit etchingof the metal part by the alkaline etchant.
 22. The etching compositionof claim 21, wherein the metal oxide is aluminum oxide.
 23. The etchingcomposition of claim 21, wherein the metal oxide is selected from thegroup consisting of hafnium oxide, zirconium oxide and mixtures thereof.24. The etching composition of claim 21, wherein the alkaline etchantcomprises an alkali metal hydroxide.
 25. The etching composition ofclaim 24, wherein the alkali metal hydroxide is at least one of sodiumhydroxide and potassium hydroxide.
 26. The etching composition of claim21, wherein the concentration of the alkaline etchant is from about 0.1M to about 10 M.
 27. The etching composition of claim 26, wherein theconcentration of the alkaline etchant is from about 0.5 M to about 1 M.28. The etching composition of claim 21, wherein the inhibitor comprisesa polyhydroxy benzene compound
 29. The etching composition of claim 21,wherein the mole ratio of inhibitor to alkaline etchant is at leastabout 1:10.
 30. The etching composition of claim 21, wherein the metalpart comprises at least one of titanium and titanium alloy.
 31. Theetching composition of claim 21, wherein the metal part comprises atleast one of stainless steel, nickel and nickel alloy.
 32. The etchingcomposition of claim 21, further comprising a stabilizer in an amounteffective to stabilize the inhibitor.
 33. The etching composition ofclaim 32, wherein the stabilizer comprises borate species.
 34. Theetching composition of claim 32, comprising: from about 0.5 M to about 1M of an alkaline etchant comprising at least one of sodium hydroxide andpotassium hydroxide; an inhibitor comprising gallic in at least a 1:10mole ratio to the alkaline etchant; and a stabilizer comprising boratespecies about 1:10 to about 10:1 mole ratio to the inhibitor.